Filters

2019 - 201912020 - 20211

More filters

20222
Reset filters

Settings

Subject: Electron tomography × WGL Institute: PDI ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Electron Tomography of Pencil-Shaped GaN/(In,Ga)N Core-Shell Nanowires
    (New York, NY [u.a.] : Springer, 2019) Nicolai, Lars; Gačević, Žarko; Calleja, Enrique; Trampert, Achim
    The three-dimensional structure of GaN/(In,Ga)N core-shell nanowires with multi-faceted pencil-shaped apex is analyzed by electron tomography using high-angle annular dark-field mode in a scanning transmission electron microscope. Selective area growth on GaN-on-sapphire templates using a patterned mask is performed by molecular beam epitaxy to obtain ordered arrays of uniform nanowires. Our results of the tomographic reconstruction allow the detailed determination of the complex morphology of the inner (In,Ga)N multi-faceted shell structure and its deviation from the perfect hexagonal symmetry. The tomogram unambiguously identifies a dot-in-a-wire configuration at the nanowire apex including the exact shape and size, as well as the spatial distribution of its chemical composition. © 2019, The Author(s).
  • Thumbnail Image
    Item
    Application of electron tomography for comprehensive determination of III-V interface properties
    (Amsterdam : Elsevier Science, 2021) Nicolai, Lars; Biermann, Klaus; Trampert, Achim
    We present an electron tomography method for the comprehensive characterization of buried III-V semiconductor interfaces that is based on chemical-sensitive high-angle annular dark-field scanning transmission electron microscopy. For this purpose, an (Al,Ga)As/GaAs multi-layer system grown by molecular beam epitaxy is used as a case study. Isoconcentration surfaces are exploited to obtain topographic height maps of 120 nm × 120 nm area, revealing the interface morphology. By applying the height-height correlation function, we are able to determine important interface properties like root mean square roughness and lateral correlation length of various interfaces of the (Al,Ga)As/GaAs system characterized by different Al concentrations. Height-difference maps based on isosurfaces corresponding to 30% and 70% of the total compositional difference at the interfaces are used to create topographic maps of the interface width and to calculate an average interface width. This methodology proves differences in the properties of direct and inverted interfaces and allows the observation of interfacial anisotropies. © 2021